A number of electrochemical techniques for detecting the presence of an analyte in a sample have been described. These techniques can be classified as catalytic, where a reaction of a modified electrode with the analyte produces a new species which can be detected electrochemically, or affinity based, where a binding reaction between the analyte and a binding partner is detected electrochemically.
When using affinity based techniques, an enduring challenge has been to detect that the binding event has occurred. Typically this is achieved using some sort of redox-labelled species that enables differentiation between before and after binding of the analyte. Typically, the redox-labelled species, labelled analyte and/or other reagents are added to the sample at some stage during the analysis in order for the binding event to be detected electrochemically. It is therefore necessary for the person using the sensor to intervene during the analysis. The need for user intervention necessitates that such sensors require skill to operate.